1. Field of the Invention
The present invention relates to a mobile unit communication apparatus which performs communication between mobile units such as vehicles.
2. Description of the Related Art
A communication apparatus which performs communication between running vehicles to exchange status information of the vehicles such as a running state is disclosed in an Unexamined Japanese Patent Publication (JP-A-5-266399). Such a communication apparatus of the related art has a radio communication device, and, through the radio communication device, performs transmission of a radio signal containing status information relating to a vehicle on which the apparatus is mounted, and reception of status information relating to another vehicle. In the communication apparatus, the transmission timing is set at given predetermined time intervals. At the transmission timing, first, it is checked whether a radio wave of a predetermined communication radio frequency exists or not. If such a radio wave does not exist, transmission at the communication radio frequency is immediately performed by the radio communication device. If such a radio wave exists, transmission is performed after the radio wave no more exists.
In a dense running environment where many vehicles are running in front and rear of the own vehicle and in the opposite direction, such a conventional apparatus for inter-vehicle communication detects a radio wave of the communication radio frequency with a higher possibility as compared with the case in a non-dense running environment where few vehicles are running in front and rear of the own vehicle and in the opposite direction. In the dense running environment, therefore, a state where plural vehicles simultaneously perform transmission to cause interference or transmission is disabled even at the transmission timing is continued, so that necessary status information cannot be immediately transmitted to another vehicle. In a dense running environment where many vehicles exist around the own vehicle, as a result, there arises a problem in that status information which is necessary for each vehicle and which relates to other vehicles cannot be efficiently obtained. In such a dense running environment, the amount of information which is received from the other vehicles and which should be processed is large, and hence there arises another problem in that the processing load is increased.
These problems are similarly produced not only in vehicles but also in mobile units of other kinds such as ships.
It is an object of the invention to provide a communication apparatus for a mobile unit which, even in the case where many other mobile units exist around the mobile unit, can efficiently obtain necessary status information relating to the other mobile units.
The mobile unit communication apparatus of the invention is an apparatus to be mounted on a mobile unit to intermittently transmit an information signal of the mobile unit. The mobile unit communication apparatus comprises: detecting means for detecting various statuses of the mobile unit and a periphery of the mobile unit, as status data; and transmission frequency controlling means for changing a transmission frequency of the information signal in accordance with the status data.
According to the invention, various statuses of a mobile unit and the periphery of the mobile unit are detected as status data, and the transmission frequency of the information signal is changed in accordance with the status data. Even when many other mobile units exist around the mobile unit, therefore, it is possible to efficiently obtain necessary status information relating to the other mobile units.